1. Field of the Invention
The present invention relates to a light-emitting device using an organic compound, and particularly to an organic light-emitting device including a layer which contains a compound having a specified molecular structure.
2. Description of the Related Art
In recent years, remarkable progress has been made in organic light-emitting devices. Organic light-emitting devices are characterized by high luminance at a low applied voltage, various emission wavelengths, high responsiveness, and are capable of being formed in thin and lightweight light-emitting devices. Therefore, there is the possibility of wide applications.
However, at present, light output with higher luminance or higher conversion efficiency is required. Also, there are many problems with durability, such as time-lapse change in long-term use, deterioration due to atmospheric gases including oxygen and humidity, and the like. Further, when applied to a full-color display, emission of blue, green, and red light, which is of high color purity, is required. However, these problems have not been sufficiently resolved.
Further, many aromatic compounds and condensed ring aromatic compounds have been investigated as fluorescent organic compounds used for luminescent layers. However, organic compounds with sufficient luminance and durability have not yet been uncovered.
Japanese Patent Laid-Open Nos. 2002-069044 and 10-189247 disclose that a compound containing a benzofluoranthene skeleton is applied to an organic light-emitting device in order to improve emission efficiency and luminance or to increase its life time (improving durability). Japanese Patent Laid-Open No. 2002-069044 discloses the application of a benzofluoranthene compound to organic light emission. Japanese Patent Laid-Open No. 10-189247 discloses the application of a benzo[k]fluoranthene compound to an organic light-emitting device. Japanese Patent Laid-Open No. 11-176573 discloses the application of a compound to an organic light-emitting device, the compound having an aromatic ring condensed at the 3- and 4-positions of a benzo[k]fluoranthene ring. Japanese Patent Laid-Open No. 2005-235633 discloses the application of a compound to an organic light-emitting device, the compound being crosslinked at the 3- and 4-positions of a benzo[k]fluoranthene ring through two nitrogen atoms.
In order to apply an organic light-emitting device to a display device such as a display, it is necessary to simultaneously secure high-luminance light output and high durability.